Telephone-transmitter.



J. P. MAXFIELD.

TELEPHONE TRANSMITTER. APPLICATION FILED JAN. 3. Isle.

1,296,683, v Patented Mar. 11,1919. 71 /i Fig. 2.

Transmitters, of which the following is a full,

To all whom it may concern:

JOSEPH P. MEXFIELD,

COMPANY, INCORPORATED, OF NEW YORK,

orrron.

OF MAPLEWOOD, NEW JERSEY, ASSIGNOR T0 WESTERE' ELECTRIC N. Y., A CORPORATION OF-NEW YORK.

TELEPHONE-TRANSMITTER.

Be it known that I, Josnrn P. MAxrrELD,

a citizen of the United States, residing at Maplewood, in the county of Essex and State of New Jersey,

and useful Improvements in Telephonegranular conducting material, directly to the action of the varying air pressure by which itoperates. By this construction the distortion, due to the fact that all diaphra ms are more or less selectively responsive, is e iminated. It

'a slightly -loss of the granules,

has been found that the microphonic actionv of a transmitter may be obtained, even in the absence of any appreciable motion of the rains, when the pressure of the gas medium etween the granules is varied, and this fact has been utllized to secure a transmitter which is particularly adapted to the faithful -re roduction of music or speech.

his invention will be more fully described in connection with the drawings, in which Figure 1 re resents a simple form of transmitter whic has been found useful in the transmission of music and speech. Fig. 2 is modified form in whiclr,,to avoid they are covered with a loose mesh ,covering, such as bolting which does not interfereappreciably with the communication of variatlons in air pres= su're directly to-the granular mass, and which communicates no appreciable motion to the grains by its vibration. Fig. 3 shows a modiation of Fig. 1. Fig. 4 a further modification by which symmetrv is obtained, and

Fig. 5 shows a commercial transmitter constructed in accordance with this invention.

Referring to Fig. 1, 1 represents a rectangular chamber, open at the top and containing the electrodes 2 and the insulating strips 3. The anular mass is contained in the space boun ed by electrodes 2 and strips 3. When this transmitter is placed in a room in which speech or music is being produced, and connected in the usual circuit, a

Specification of Letters Patent.

have invented certain new silk,

Patented Mar. 11, 1919.

Ap flication filed January 8,1916. Serial No. 89,947.

very high quality of reproduction is obtained and the source of sound may be located at a considerable distance from the transmitter.

Fig. 2is similar to Fig. 1, except that the granules are retained by the covering 4, which should be so porous that there is offered the least obstruction to the transfer of air pressure through it consistent with its object, which is to prevent loss of granules in transportation and handling.

In Fig. 3 the transmitter of Fig. 1 is modified'by the addition ofthe insulating strip 5 which divides the chamber into two parts. It has been found that this adds somewhat to the efiiciency of the device when it is used in a position other than horizontal.

Fig- -1-is a modification of Fig, 2 which eliminates one objection to Fig. .2, namely,

that when it is used in a vertical pla'ne, the

. amount of the granular mass. in contact with the electrodes, depends upon the vertical angle through which the device is turned. In Fig. 4: the electrode 2 has the form of a ring, as shown, while the complementary electrode 2 is located at the center of this ring. By this means the amount of granular material incontact with the electrodes is independent of the angle through which the device may be turnedabout an axis of symmetry: In this figure, as well as inf'Fig. 2, the purpose of the coverin 4 is not to transmit motionto thegranu es,'but merely to retain them, and for this reason it should be so constructed as. to expose as small a surface as possible to the incoming waves. It has been found that a very loose mesh silk covering is suitable for mesh being as large as is ossible without allowin the grains to fall through.

Fig. 0 shows the rectangular box of Fig. 2 mounted ina commercial transmitter. It is clear that any one ofthe other transmitters shown in these drawings may be substituted, and in fact it will usually be desirable to make use of the transmitter of Fig. 4 for this urpose.

W at is claimed is: 1. A telephone transmitter comprising a chamber containing electrodes and a resistance comprising a granula conducting material between said electrodes, and means for exposing said granules to the direct action of aerial sound waves whereby the value of said resistance is controlled in accordance therewith.

this purpose, the

2. A telephone transmitter comprising an open chamber containing" electrodes and granular conducting material, the said material forming directly the receiving element for aerial sound waves Without the intermediary of a vibrating diaphragm attached to one of said electrodes.

.8. A telephone transmitter comprising a chamber, electrodes and granular conducting material in said-chamber, and a loose mesh covering for said chamber through which aerial disturbances are transmitted to the granular mass without the intermediary of a vibrating diaphragm attached to one of said electrodes.

4. A telephone-transmitter comprising a chamber, electrodes and granular conducting material in said chamber, and a porous gauze covering whereby the granular mass is retained and the said inclosed mass is directly exposed to aerial disturbances without the intermediary of a vibrating diaphragm attached to one of said electrodes.

5. A telephone transmitter comprising a greases turbanoe's may penetrate without substantial obstruction and afi'ect directly said granular material without the intermediary of a vibrating diaphragm attached to one of said electrodes.

7 A telephone transmitter comprising a chamber containing two non-vibrating electrodes and a; granular conducting material between said electrodes exposed directly to aerial sound waves.

8. A telephone transmitter comprising a chamber containing two electrodes substantially nonresponsive to sound vibrations, and a granular conductin material between said electrodes exposed directly to aerial sound waves.

9. A telephone transmitter comprising a chamber, electrodes and a granular conducting material in said chamber, said electrodes being substantially nonresponsive to sound vibration s,]"and a loose mesh covering said chamber through which aerial disturbances are transmitted to the granular mass.

10. A telephone transmitter comprising a chamber containing electrodes and a variable resistance comprising a granular conductin material between said electrodes controfied in value by the amount of air pressure thereon, the open face of said chamber being covered by a porous gauze I whereby the granular mass may be retained.

In witness whereof, I hereunto subscribe my name this 30th day of December, A. D.

JOSEPH P. MAXFIELD. 

